/Engine/Source/Runtime/ImageWrapper/Public/Formats/HdrImageWrapper.h
this is often broken, should only be used with InFormat ==GetFormat()DEPRECATED , useGetRaw()with 1 argument orGetRawImage()true on success, false otherwise.
virtual bool GetRaw ( const ERGBFormat InFormat, int32 InBitDepth, TArray64< uint8 > & OutRawData )